Method of preparing metals for electroplating



WW Set ea tea arm METHOD OF EREPARING METALS F ELECMQPMTJING- No Drawing.

the metal that it will receive a uniform, ad-

herent electrodeposit of another metal that will not blister or peel.

Considerable difiiculty has been encountered heretofore in electroplating steel, cast W iron, wrought iron, chilled iron or other ferrous bodies due to the tendency of the electrolytically deposited coating to peel, to blister, to crack off, or to otherwise fall in intimate adherence to the metallic body. While many methods of pretreating the bodies to be electrocoated have been suggested, most of them are of limited usefulness, being applicable to only one class of ferrous materials or being of too great complexity or of uncertain performance.

After extensive investigation, .it has been found that treating, preferably by scouring, the surface of the metal to be plated with an oxidizing material, greatly improves the character and quality of the subsequent electrodeposit in respect of uniformity and satisfactory adherence. With the application of the method, steel, chilled iron and cast iron have been successfully electroplated with copper, nickel or chromium, or with combinations of these metals, without any of the defects of the character hereinbefore indicated developing, while, in the absence of this pretreatment, one or more of the defects almost inevitably appear.

In the application of the method of preparing the metals for electroplating, the surfaces to be plated are cleaned of grease, oil, dirt or other adherent foreign material by any suitable means, after which any rust or any other oxidation products are removed by pickling in an acid solution, following which the surface is treated, preferably by scouring, with a suitable oxidizing material. Finally, the oxidizing material is washed or rinsed off and the metal body is ready to receive a uniformly adherent electrolytic deposit of the desired metal.

It has been found that various oxidizin agents may be employed, such as Na CrO of the inert material is Application filed September 3, 1930.. Serial No. 479,584.

Na Cr 0 K Cr0 K Cr O CrO n0 NaMnO K010 KNO NaClO NaNOa, in any-degree of concentration or any various combinations. Some of the agents, either alone or in combination, may be made up in the form of a paste by admixing the same with water, or, if desired, they may be applied as a dilute aqueous solution. A convenient form of applying the oxidizing agent is in the form of a paste made up of a solution of one or more of the oxidizing agents, with a suitable inert material, such as pumice, whiting, ground chalk or fine sand. The particular advantage of'using such an inert material is that it enables a dilute solution of the oxidizing agent to be employed and which the inert material holds in contact with the surface under treatment for any desired length of time. Another advantage that it has in itself some mechanical cleansing effect on the metal surfaces, particularly when the compound is applied thereto by a scouring operation.

As a specific illustration of the application of the invention to electroplating a chilled iron roll. with a uniform deposit of chromium, the chilled iron roll was first washed with an organic solvent, to remove the grease'and oil and was then swabbed with pumice and ahot solution of a mild alkali. The roll was then pickled for five minutes in a solution of one part of concentrated commercial hydrochloric acid in four parts of water. The roll was then rinsed with water and swabbed with commercial hydrochloric acid and again rinsed. The. roll was then swabbed with a paste made of whiting and a 10% solution of potassium permanganate (KMnO This paste was allowed to remain on the surface of the roll for five minutes, after which it was washed off. The roll was then put in a chromium plating bath and plated for three hours with a current density of two amperes per square inch, with the result that a firmly adherent uniform coating of chromium was 9 applied to the treated surface of the roll.

What I claim is:

1. A- method for the treatment of ferrous metals which comprises removing adherent foreign material from the Surface of the Cal F scouring the said sur metal, scouring the said surface with an abrasive material containing an oxidizing agent, removing said abrasive material from the said-surface and then electroplating the said metal.

2. A method for the treatment of ferrous metals which comprises scouring the said surface with an inert abrasive material containing a non-acid oxidizing agent, removing said scouring material from the said surface and then electroplating the said metal.

3. A method for the treatment of ferrous metals which comprises treating the metal to remove grease and other foreign material from the surface thereof, scouring the said surface with an abrasive material containin an aqueous solution of an oxidizing agent 6 the group consisting of alkali metal chromates, chlorates, permanganates and nitrates, removing said scouring material from the said surface and then electroplating the sotreated metal.

4. A method for the treatment of ferrous metals which comprises treating the said metal to remove grease and other adherent foreign material from the surface thereof;

scouring the said surface with an abrasive material containing an aqueous solution of a permanganate, removing said abrasive ma= terial from the said surface and then electroplating the said metal.

5. A method for theItreatment of ferrous metals which comprises treating the. said metal with a solvent to remove grease and other foreign material from the surface thereof, scouring the said surface with an inert abrasive material containing a non-acid ox1d1z1ng agent so as to render the surface of 40 the metal receptive to plating by electrolysis,

removin the said scouring material from the said sur ace and then electroplating the said metal.

6. A method for the treatment of ferrous metal objects which comprises treating the metal object with a solvent to remove grease and other foreign material from the surface thereof, immersing the said object in a pickling bath containing hydrochloric acid,

ace with an inert abrasive material containing calcium carbonate and an aqueous solution of potassium permanganate, washing the said object to remove the said scouring material therefrom and then electroplating the said object in a suitable plating solution.

In testimony whereof I aflix my signature. ARTHUR F. FRANCIS. 

